Merriam-Webster Collegiate Dictionary - three

 noun  Etymology: Middle English, from ~, adjective, from Old English thrie (masculine), threo (feminine & neuter); akin to Old High German dri ~, Latin tres, Greek treis  Date: before 12th century  1. — see number table  2. the third in a set or series the ~ of hearts  3.  a. something having ~ units or members  b. ~-pointer  • ~ adjective  • ~ pronoun, plural in construction